Saturday, February 04, 2006

Cape Horn Slope

From: "Jack Duncan"

[The slope at] Cape Horn ... is ... approximately 45 degrees. My measurements at 18 locations along the 1,000 foot construction zone varied from 28 degrees to 51 degrees. These are slopes at right angles to the tracks. The slopes below the tracks are considerably steeper. For instance, I estimate the slope at the ladder in Figures 61 and 62 in my book to be about 60 degrees. That being below the tracks, only the retaining wall masons had to contend with that slope. That is too steep to work on without a ladder or a rope but no need for a basket or bosun's chair.

Mentioning the 38 degrees talus slope below ... may lead [people] to think that the slope below is 38 degrees. That is far from the truth. Shortly below the work site the slope increases to 60 degrees and 75 degrees and maybe steeper for a short distance. Below that steeper region, the slope "flattens out" and even becomes level briefly near Robber's Creek. That "leveling out" area is actually an extension of Burnt Flat. That "lesser slope" is where the disposed shale pieces stopped resulting in a talus slope of about 38 degrees down there. That has no relationship to the approximately 45 degrees at the railroad construction site. No workers were needed down there in 1865. At the bottom of the talus is where the tumbled automobiles and household appliances stopped tumbling in recent years. The talus consists of uncemented shale plates like "1 inch thick shoe soles," which as you know, makes walking up the slope very difficult, like climbing a sand pile. That talus material can not build on a slope greater than the 38 degrees, therefore, the talus exists 300 feet to 500 feet below the railroad, not immediately below the grade. It's too steep close below the railroad.

My discussion of shale at "West Cape Horn" is entirely different. Along that side hill the slope above the RR is about 40 degrees but the ravines below into Rice's Ravine are more like 30 degrees. That allowed the 35-38 degrees talus to build up fills without the need for retaining walls.

These numbers ... are ... in my book "A Study of Cape Horn Construction." Quoting the 38 degrees could lead [people] to jump from the wicker basket nonsense to an opposite extreme of believing that the gentle hillside is only 38 degrees at the edge of the road bed. Not true. ...

—Jack Duncan